This invention relates to catalysts, and more particularly, to platinum catalysts for oxidizing ammonia in vapor phase catalytic ammonia removal systems.
Catalytic systems are widely known and used for decomposing or oxidizing undesirable chemical species within a fluid. Catalytic systems are used in space vehicles and in space stations to remove ammonia and other chemicals from waste streams generated during a space mission. Typically, water-based waste streams are collected, distilled, and purified before being reused by a crew. The weight of such catalytic systems and the amount of energy that the catalytic systems use is minimized to reduce relatively high expenses related to space travel.
Conventional catalysts typically include an active metal deposited on a support material. Typically, the type of active metal and type of support material are selected based upon the application that the catalyst will be used in. Disadvantageously, currently available combinations of active metals and support materials for ammonia oxidation require temperatures above approximately 200° C. to oxidize ammonia and often result in the formation of nitrogen oxide (NOx. To minimize NOx formation, the catalyst is undesirably operated in a narrow temperature range above the catalysis activation temperature and below the NOx formation temperature.
Accordingly, there is a need for an ammonia catalyst that operates over a relatively large temperature range and at temperatures below 200° C. to avoid the formation of NOx.